Synthesis of melt-spun rare-earth transition-metal intermetallics with Nd3(Fe,Ti)29-type structure

Rare-earth transition-metal intermetallics with the Nd3(Fe,Ti)29-type structure with R=Nd, Pr have been synthesized. The as-spun ribbons show a broad magnetic transition between 400 and 500 K. After annealing over a range of temperatures, 723-1373 K, and for times in the range 15-50 min, multiphase samples with the R3(Fe,Ti)29, R(Fe,Ti)12, R2(Fe,Ti)17 and α-Fe phases are obtained. The optimum conditions are: for R=Nd the samples spun with a velocity of 30 m s-1 and annealed at 1373 K for 25 min contain Nd3(Fe,Ti)29 as a main phase, 67 wt.%, with some Nd(Fe,Ti)12 and α-Fe; for R=Pr the samples spun with a velocity of 20 m s-1 and annealed at 1323 K for 25 min contain 88 wt.% Pr3(Fe,Ti)29 with some Pr2(Fe,Ti)17 and α-Fe. These samples present Curie temperatures typical for the Nd3(Fe,Ti)29 and Pr3(Fe,Ti)29 compounds. The room-temperature saturation magnetization is 124.2 and 138.7 A m2 kg-1 for R=Nd and 135.0 and 118.9 A m2 kg-1 for R=Pr, before and after annealing, respectively. The annealed ribbons show grain sizes of <1 μm, and a mean stoichiometry of Nd3Fe24Ti5 and Pr3Fe26.5Ti2.5 for the 3:29 phase. The annealed samples present low coercivity values attributed to the presence of the soft α-Fe phase. (orig.)